Dental hand piece



Jan., ,223, 3951 M. sTAuNT 2,538,923

DENTAL HAND PIECE Original Filed Sept. 13, 1945 @d6/Z077 .Marijn Smid;

Patented Jan. 23, 1951 UNITED STATES ATENT OFFICE Original application September 13, 1945, Serial Divided and this application Maloh l2, 1948, Serial No. 14,561

1 Claim. l

The present invention relates to dental hand pieces, and is particularly concerned with dental hand pieces of the type which are to be driven by means of a belt and pulley, and which embody an improved form of swivel frame.

The present application is a division of my prior application, Ser. No. 616,130, filed September 13, 1945, now Patent No. 2,445,891, for Dental Hand Pieces; and is particularly concerned with the lubricated pulley structure` .is-closed in my prior application.

The present application is related to my prior application, Ser. No. 734,383, filed March 13, 1947, now Patent No. 2,529,824, which prior application relates to the structure shown in Fig. l and the lower` part of Fig. l; and the structure shown in Figs. 2 and 3 and the upper part of Fig. 1 are unclaimed in said prior application.

One of the objects of the invention is the provision cf an improved lubricated pulley structure by means of which the pulleys are not only suitably lubricated, but they are guarded so that no rotating parts are exposed toward the outside which might engage the clothing of the user.

Another object of the invention is the provision of an improved pulley structure which is simple in construction, sturdy, capable of being manufactured at a low cost, and which may be maintained in a well lubricated condition at all times.

One of the objects of the invention is the pron vision of an improved dental hand piece of the i class described, in which improved forms of benings are utilized, which, by virtue of the particular material utilized in the spindle, permit the use of relatively small bearings; but the bearings may be used for a long period of time without substantial wear,

1 splashing of the oil and for the quick removal 5 of the pulley` by of threaded gland that holds the tightening rod and threaded shaft.

Ancther object of the invention is the provision of an improved Wrist joint structure, including a stop for limiting the rotative motion at the Wrist l joint, which is adapted to be manufactured more V, economically, and which is easy to attach and easy to remove for use with other attachments..

Another object of the invention is the provision of an improved streamlined structure from which the sharp corners have been removed so much that the mouth of the patient and the hands of the operators are more effectively protected against injury.

Another object of the invention is the provision of an improved stop for limiting rotative motion at the wrist joint, all of the parts of which are housed in suitable recesses so that there are no projecting` parts and therx are no sharp parts which rub against the belt and tend to wear it.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings, in Which similar characters of reference indicate similar parts throughout the several views.

Referring the single sheet of drawings,

Fig. l is a side elevational view of a dental hand piece embodying my invention;

Fig. 2 is a fragmentary axial sectional view of the operating end of the hand piece;

Fig. 3 is another fragmentary axial sectional view of the rear end portion of the hand piece; and

Fig. 4 is a fragmentary sectional View, taken on a plane passing through the axis of the pulleys, that is, the plane along the line of Fig. 1.

The dental hand niece embodying my invention is shown in side elevation in Fig. l, and is indicated in its entirety by the numeral Il). It preferably includes a sheath ll, which may consist of a tubular metal member preferably made of stainless steel or carbon steel, having an axial bore i2 and an external cylindrical surface I3, which is provided with a multiplicity of partially circular parallel grooves Ill.

The ridge portions or cylindrical surfaces i3 between the grooves are preferably knurled for nonslipping grip with the lingers; and the provision of grooves and ribs alsa aids in permitting internal threads i5 forengagement with the external threads i3 on the fr^nt bearing member l1.

The member Il is preferably constructed of case hardened screw steel stock. The front bearing member il preferably consists of a tubular metal member, the external surfaces of which are tapered at i8 and i9 toward the open end, which has a bore il?.

The front bearing member I1 has a tapered counterbore 2l, which serves as a front end bearing for the spindle 22, which has a complementary external frusto-conical surface 23. The front bearing member I1 also has an annular shoulder 24, against which the end of the sheath Ii abuts when it is threaded home by means of the threads I5, I6. At one side the front bearing member is preferably provided with a threaded bore 25, extending radially, and adapted to receive the screw bolt by means of which other attachments are secured to the front end of the hand piece, in such manner that the attachment housing does not rotate. Such attachments preferably have a spindle that is held in the chuck and a housing that slides on the nose of the hand piece, and have a slot for the screw bolt 25.

The front bearing member I1 is provided with a cylindrical bearing sleeve Ila, having a frictional t in a complementary recess located at the cylindrical end portion of the front bearing member I1, that is, at the right end, beneath the threads I5.

The spindle 22 is preferably made of steel which is initially plated with a layer of chromium, such as, for example, five thousandths of an inch thick. This chromium covered steel spindle may be ground down until its chromium covering is substantially three thousandths in grinding the spindle to t the bearings.

The bearing sleeve I1a is preferably constructed of a hard alloy; and such a combination of chromium plated spindle and hard alloy bearing is adapted to give long use with a minimum amount of wear or vibration.

The spindle 22 is preferably cylindrical on its outer surface, inside the bearing sleeve I1a, but also preferably has a taper extending from said bearing sleeve toward the end of the spindle, where a relatively sharp tapered surface 23a is provided. The internal surface of the bearing member I1Y is complementary in shape.

The spindle comprises an elongated metal member, which is tubular in shape. Over the major portion of its length it has an external cylindrical surface 25. It is provided with an internal cylindrical bore 21, which terminates at the front end in a frusto-conical surface 28 for engaging one end of the collet 29.

The collet 29 is adapted to grip the stem of a burr or the shank of a sanding wheel, or any other tool; and it consists of a substantially tubular metal member having the external cylindrical surfaces 39, 3l, 32.

The collet 29 has a cylindrical through bore 33, which is approximately the same size as the shank which it is intended to receive, having a close sliding t with the shank. Each end portion of the collet is provided with a plurality, preferably three, axially extending slots 34, 35, the slots being equally spaced in an angular sense and separating the end portions of the collet into three separate legs.

The external body of the collet is preferably grooved or relieved at and 31 adjacent the end portions so as to increase the flexibility of the legs, which are formed by the slots 34, 35, adjacent the base of the slots. At each end of the collet there is a tap-ered or frusto-conical portion 38, 39, which, when engaged by a complementary frusto-conical surface, may tend to cause the end portions of the collet to contract and to grip a shank in the bore 33.

The'frusto-conical surface on the front end of the collet at 38 engages the complementary frusto-conical surface 28 inside the spindle. The

frusta-conical surface 39 at the other end of the collet, that is, the right end (Fig. 2), engages a complementary inner frueto-conical surface 40 on a plunger 4 I.

The plunger 4I merely consists of a cylindrical metal member having a sliding fit in the bore 21 of the spindle 22. The right end 42 of the plunger may have a plane surface, while the opposite end preferably has a bore 43; and the annular end surface terminates in the frusto-conical surface 40, previously mentioned.

The natural tendency of the collet is for its end portions to spring outwardly into cylindrical form; but, when forced toward the left in Fig. 2 by the plunger 4I, the end portions of the collet are cammed inwardly toward each other, diminishing the size of the slots 34, 35, while the collet grips a shank.

The spindle bore 21 also houses the tightening rod 44, consisting of an elongated metal rod having a plane end surface 45 for abutting against the end 42 of the plunger 4I. Adjacent the end 45 the tightening rod 44 has a cylindrical enlargement 46, which has a sliding t in the spindle bore 21 and centers the tightening rod at this end. At its opposite end in Fig. 3 the tightening rod 44 has a threaded portion 41, the threads of which are complementary to the internal threads 48 in a threaded gland 49, the threaded portion 50 of which engages the internal threads 5I in the end of the tubular spindle 22.

A steel knob 52 may be threaded on the end of the tightening rod 44 by means of a threaded bore 53, and may be secured in place by being soldered to the rod 4-4 or by a frictional pin 54, which passes through both the knob and the threaded portion of the tightening rod 44. The cylindrical edge surface 55 of the knob 52 is preferably knurled; and the length of the threaded portion 41 is such as to permit longitudinal adjustment of the tightening rod 44 by means of its threads 41.

The gland 49 has a radially extending flange provided with a cylindrical knurled surface 56;

but at two diametrically opposite points on the gland 49 there are parallel flat surfaces 51 for engagement with a small wrench.

The spindle 22 (Fig. 3) may be provided with a cylindrical thrust ring 58 pressed on the spindle, and has an annular surface 59 serving as a thrust bearing. Beyond the thrust surface 59 and toward the right in Fig. 3 the spindle 22 has a reduced cylindrical portion 60, which serves as a trunnion for engagement in the cylindrical bore 6I of the rear bearing 52.

This rear bearing member G2 is also preferably constructed of hardened steel or bronze, and is provided with an annular lubricant groove 63 communicating with a radial aperture 64. This aperture communicates with a plurality of radially extending apertures 65, regularly spaced about the periphery of the rear bearing member E3.

These apertures 65 communicate with an annular slot a in the inner threaded surfacey 58 of the wrist joint frame so that the aperture 55 will be constantly in communication through the slot 65a with the apertures 64, even though the wrist joint is adjusted longitudinally on the rear bearing member. Lubricant, which enters at 65, finds its way about the spindle 22 in the annular groove 63, from which it spreads longitudinally on the cylindrical trunnion 60 in- Side the cylindrical bearing 62.

The rear bearing 62 has a substantially cylindrical threaded member 67 adapted to be received in the threaded bore 88 of the wrist joint frame. At the left, beyond the wrist joint frame,

the rear bearing 62 has an enlarged cylindrical portion B9, which has a substantial t in the cylindrical bore I2 of the sheath I I.

The bore 6| of the rear bearing 62 communicates with an enlarged counterbore 10, beginning at the thrust washer 58, where there is an annular thrust surface '1| engaging the thrust surface 59 on the thrust washer 58.

To the left of the thrust washer 58 the spindle l22 is substantially smaller than the bore 'Ill in the rear bearing 62 or the bore I2 in the sheath 2.

II. The cylindrical skirt I2 on the rear bearing S2 extends into an enlarged counterbore 'I3 in the sheath II; and the length of these two complementary members, that is, this portion of the sheath and the skirt on the bearing, serves to hold the bearing accurately in concentric position with respect to the sheath.

The wrist joint frame is also preferably provided with a radially extending threaded bore M (Fig. 3) having a screw bolt 'I5 which engages a slug l, driving it into tight engagement with the threads 61 to maintain the adjustment of the wrist joint frame on the bearing B2.

The slug 'I6 has at its end threaded formations complementary to the threads 6l so that :ti

the set screw I5 may clamp the slug 'i6 against the threads 8l without deforming or mutilating the threads. The slug 'I5 is of the same shape at it-s end as the threads and, as it does not rotate, it does not mutilate the threads.

There is rotating engagement between the slug I5 and the screw bolt l5, which preferably has a slot for receiving the screw driver or tool.

It is by means of the adjustment of the wrist joint frame 56 on the threads 57 that bearing wear may be taken up at the front bearings ll, as a longitudinal adjustment of the spindle 22 toward this* iront bearing will cause the tapered surfaces 23 on the spindle 22 and on the bearing Il to come into closer engagement with each other to take up wear.

The sheath I3 is provided with a radially extending securing flange 'I'I and a plane end surface I8 that abuts against the plane end gurface 'I9 on the wrist joint frame 65. The radial flange ll is preferably circular and adapted to be received in the bore 8i! of aA union nut 3|, which has an external cylindrical knurled surface 82. The nut il has threads 83 in the bore 82 for engaging threads 84 on the left end of the wrist joint frame (Fig. 3). 1

An annular surface 85 on the inside of the bore 1Q of the union nut Si engages the radial ange 'VI and draws the sheath I! into tight engagement with the wrist joint frame 65. The union nut 8| has a bore 86 for receiving the smooth cylindrical body portion 8l of the sheath II.

rThe spindle 22 has a pulley 88 xedly secured to the right end of the spindle by means of gland 49, the annular surface 89 of which engages the end of the hub @D of the pulley 88. `The pulley 88 has a cylindrical bore9! having a sliding fit on theright end of spindle 22 (Fig. 3).

The spindle 22 preferably has a partially cylindrical groove S2 extending in an axial direction adapted to receive the pin 93, which is driven into a bore Sli in the hub 90 of the pulley 88 in such manner1 that the pin abuts against the end of the bore 94 and projects radially into the bore 90 of the pulley S8 so that it may be received in the groove 93.

The bore Sli is actually in the shape of a groove of cylindrical shape embodying more than half of a cylindrical recess so as to retain the pin 93 in the hub when the pulley 88 is removed. Furthermore, the pin is driven tightly into the hub and substantially riveted and expanded therein. Thus the pulley 83 is prevented from rotating with respect` to the spindle 22; and it is held on the spindle 22 by the gland 49.

The rear bearing 62 preferably has a tubular extension which is externally threaded at 96, extending inside the bore tl, which is provided by an axially extending tubular skirt 98. This skirt 98 prevents any lubricant which might nd its way out of the bearing 62 from splashing; and leakage is further reduced by the fact that the lubricant must pass along the threaded surface 96 to get on the outside of the bearing 62.

The pulley 88 preferably has a pair of pulley flanges .99, |88, which iiare outwardly away from each other and have cylindrical outer surfaces IllI. The adjacent inner surfaces |02, |03 form a V-shaped groove, which bells outward at the edge of the pulley so as to insure the engagement with the belt and a tight driving engagement by the belt wedging into the groove |84.

The wrist joint frame has a supporting arm |05, which extends radially outward from the body portion having the bore 53 and preferably curves through substantially ninety degrees. The arm |65 supports a cylindrical portion |55 that extends at right angles to the spindle 22; and the cylindrical portion |96 has an axial bore |81. This axial bore provides a bearing for the trunnion |88 of the wrist joint swivel arm `ID9.

In order to retain the trunnion |28 in the bearing |81 and to limit its motion the trunnion |538 is provided with an arcuate slot llt of limited length extending over substantially 270 degrees and apadted to receive the reduced cylindrical end |I| of a screw bolt H2, which is threaded into a thre-aded bore Ils located in the bearing |06.

Thus the wrist joint swivel arm |89 may turn until the end Iii of the screw bolt ||2 engages either end of the slot IIU. Axial movement of the trunnion Ill in the bearing |915 is prevented by the screw bolt ||2 in the slot ||8.

rIhe wrist joint swivel arm has a flattened Vend portion |Ill, which is pivotally mounted inra wrist joint swivel frame i l5 by means of a screw bolt IIS. The wrist joint swivel frame comprises a ilat metal member ci substantially triangular form, which is provided with a slot ill, which is rectangular in shape and is bounded by e pair of flat parallel flanges H8 and l I9.

yThe slot |I'l over the full length of the base ld of the triangle and substantially half way up both of the other sides of the triangle is adapted to receive the ilattened end portions lill, 52| of the front wrist joint swivel arm |55 and the rear wrist joint swivel arm |22.

The latter is pivoted on the wrist joint swivel frame by means of the screw bolt |23. The screwY bolts H55 and |23 have their heads embedded in counterbores in the upper flange lle (Fig. 1) and 4have cylindrical portions adapted to serve as trunnions or pintles located in the slot II'I and threaded portions threaded into threaded bores in the lower flange I I8, as indicated in dotted lines in Fig. 4.

The intermediate pin |26.. is riveted in both of the flanges H8, H9 and passed through the slot midway between the two screw bolts I6, |23 and serves as a stop for engaging the flat shoulder |25 on each of the pivot flanges lili, |2| of the wrist joint swivel arms. The remainder of the edge of the pivot flange is substantially circular, as indicated at |25, so as to clear the pin |24. Thus the wrist joint swivel arms can move to a position where they are almost in line with each other or tov a position in which they extend at an acute angle, as shown in Fig. 1, permitting the maximum freedom of movement of the hand piece itself in the hands of the operator.

The rear wrist joint swivel arm |22 is provided with an axial bore |27, which extends rearwardly to a point past the radial aperture |28, into which the inwardly turned end of a leaf spring |29 extends.

The leaf spring is preferably secured in a groove |30 by having a screw bolt |3| pass through the end of the leaf spring, the bolt being threaded into the arm |22. At its end the tubular arm |22 has an axially extending, partially annular portion |32, which engages in a slot complementary to it on the arm, to which it is attached, this arm having a shank that passes into the bore I 2, and having a hole for receiving the end of the spring |29. l

The wrist joint swivel frame ||5 is shown in section in Fig. 4; and this frame also serves to support a pair of pulleys |33, |34, by means of a wrist joint pulley stud |35. The body of the wrist joint pulley frame IIS has a through bore |36, into which the stud is forced, the stud being provided with axially extending knurled formations by means of which it is secured against rotation with a pressed t. At each end the pulley stud has a reduced cylindrical portion |31, which serves to receive a thrust washer |38 that spaces the pulley from the frame H5, and is engaged by the pulley shaft.

The pulley stud |35 has each end provided with a reduced threaded portion |39, which is adapted to be received in the threaded bore |40 of the pulley shaft Ilil.

rlhe pulley shaft comprises a substantially cylindrical metal member, which has the threaded bore ille, and a smaller counterbore |42 for lubrication, the counterbore |42 being spun over at its end |43 to retain a steel ball ld, which is urged into engagement with the spun-over portion |43 by a compression spring l the other end of the spring engaging the reduced threaded end i3d of the pulley stud.

The pulley shaft also has a radially extending aperture MG whereby lubricant which is forced in past the ball |44 may gain access to the external cylindrical bearing surface l 4l of the shaft fdl. The shaft lf3! also supports a pulley guard |48 in the form of a substantially circular radially extending flange carried by the pulley shaft |4|, which extends beyond the edge of the pulley |34 and has an inwardly extending cylindrical flange lf overhanging the cuter flange of the pulley.

The guard Hi8 protects the hands of the operator from the pulleys; but it does not interfere with the pulley belt, and the guard also prevents the throwing of oil, which might be carried by the pulley to its outermost edge by centrifugal force.

The pulley guard preferably has an annular thrust surface E 5S located to engage the outer end of each pulley so that endwise motion of the pulley on the pulley shaft is prevented; and the pulley has a running t between the washer |38 and the thrust surface |59.

The two pulleys may be identical in construction, and each consists of a circular metal member provided with a centrally located bearing bore |5| for receiving the pulley shaft on which the pulley has a freely rotating t. At is periphery the pulley is provided with a partially circular groove |52, which is bordered by two radially extending pulley flanges |53, i.

The belt passes over one of the pulleys |33 to the drive pulley 88, and thence back over the other pulley |34 to the usual motor driving mechanism.

It will thus be observed that I have invented an improved dental hand piece which is provided with improved bearing structures by means of which the hand piece operates more smoothly and may be maintained in most excellentl condition for a long pe 'iod of time without repair.

The pulley is quickly detachable, being held in place by a threaded gland, which also serves to support the tightening rod by means of which the collet of the chuck may be controlled for gripping the shank of a tool.

The present hand piece has its wrist joint frame adjustably supported in such manner that wear of the bearings may be taken up; and adequate provision is made for maintaining proper lubrication of the spindle at all times.

The wrist joint frame arm is provided with an improved built-in form of stop, which may be more cheaply manufactured, and which has no projecting parts that might catch on the clothing 0f the operator. The wrist joint pulleys are guarded and protected on both sides, and are provided with adequate means for assuring their lubrication at all times and for preventing the pulleys from throwing off lubricant on the operator or the patient.

The present hand piece may be taken apart very easily for inspection of its parts or for cleaning; and it is also adapted to be maintained in a sanitary condition with a minimum amount of labor.

While I have illustrated a preferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but de sire to avail myself of all changes within the scope of the appended claim.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

In a dental hand piece, the -combination of a tubular housing having an external surface comprising a multiplicity of longitudinally spaced annular lands, the said lands being knurled and separated by partially circular grooves, said housing having a radially projecting ange at its rear end, an inwardly threaded ferrule slidably and rotatably mounted on said housing and engaging said flange, a bearing in said housing, said bearing having an externally threaded surface, a

-wrist joint having a threaded bore threaded on said bearing, said wrist joint also having an externally threaded surface, said ferrule being threaded on said latter surface of said wrist joint, said wrist joint having a radially threaded bore extending from its outside to said bearing, a set screw in said radially threaded bore, and a dcformable slug in said radial bore and driven by said set screw into engagement with the threads of said bearing, said slug being held against ro- 9 tation by said threads, and said set screw rotating against said slug to place a pressure on said slug against the threads of said bearing, to maintain the threaded adjustment of the bearing Without damaging the threads on the bearing. 5

MARTIN STAUNT.

REFERENCES CITED The following references are of record in the lo le of this patent:

Number Number 10 UNITED STATES PATENTS Name Date Bonwill Nov. 11, 1890 Bates Apr. 13, 1920 Pieper Dec. 8, 1931 Angell Jan. 5, 1932 Staunt Nov. 9, 1937 Staunt July 15, 15H1 Staunt Dec. 9, 1947 FOREIGN PATENTS Country Date Great Britain Aug. 27, 1931 

